Needle valves are known in the art for controlling fluid flow through a pathway of reduced diameter relative to the inlet and outlet orifices, for example. Flow is typically in one direction, and a user can typically restrict or increase the flow rate through the valve and bring the flow to a desired level. In some circumstances, flow may be limited to one or more drops over a period of time.
As shown in FIG. 1, a needle valve 10 of the prior art is shown. The prior art valve 10 of FIG. 1 includes a body 12, a seat 14, an o-ring 16, a stem 18, a bonnet 20, and a thumbwheel 22. The seat 14 of the prior art valve 10 of FIG. 1 is integrally attached to the body 12 at an internal cavity thereof, which can be achieved through molding the seat 14 in place against the body 12. During operation of the prior art valve 10 of FIG. 1, a user rotates the thumbwheel 22 causing the stem 18 to be driven downward through the bonnet 20, where a distal end of the stem 18 alternately engages/disengages the molded-in-place seat 14. The stem 18 imparts compressive loads on the seat 14, resulting in a seal restricting flow through the body 12. This type of stem 18 is known as a “rising stem” type.
The body 12 of the prior art valve 10 of FIG. 1 is one piece with a geometry that includes an inlet, outlet, top entry port, and internal flow path. The top entry port of the prior art valve 10 of FIG. 1 allows for the insertion of an assembly comprised of the stem 18 and bonnet 20. The top entry port of the prior art valve 10 of FIG. 1 contains female threading which engages the male threading of the bonnet 20, securing the bonnet 20 thereto. Alternatively, it is known in the art for a bonnet and a top entry port to be connected through a flanged configuration. The bonnet 20 of FIG. 1, has internal female threading which engages the male threading of the stem 18. This allows for a user to rotate the thumbwheel 22, attached to one end of the stem 18, and drive the stem 18 downward through the bonnet 20, or lift it upward. It is known in the art to attach the thumbwheel 22 to the stem 18 using ultrasonic welding. The stem 18 can be driven to a fully downward position, at which point the stem 18 engages a seat 14.
Referring to FIG. 1, it is known in the art for the seat 14 to be molded with or otherwise physically attached to the valve body 12. FIG. 1 shows a molded-in-place seat 14 which is affixed to the interior of the body 12. In such an arrangement, when the stem 18 is driven fully downward it engages the seat 14 and, through compressive loads imparted on the seat 14, seals the orifice restricting the flow through the valve 10.
It is known in the art to provide seats that are integrally formed with, attached to, and/or assembled with a valve body. It is also known in the art to provide seats that are integrally formed with, attached to, and/or assembled with a valve stem. Attachment of the seat might include fasteners, adhesives, sleeves, press-fits, or over-molding of malleable rubber or plastic materials onto rigid metal or plastic substrates. However, what is needed in the art are systems and methods for improvements to the seats of needle valves.